1. Field of the Invention
The present invention relates to a meter of the type having crossed coils.
2. Description of the Prior Art
Meters of the type having crossed coils are well known and comprise a magnet, a pointer shaft having one end extending through the magnet at a center portion thereof and attached thereto for integral rotation, a pointer attached to the opposite end of the shaft, a pair of upper and lower housings, each being made of a non-magnetic material, such as a plastic, which mate with each other to rotatably carry the magnet and the pointer shaft, a pair of crossed coils winding the housings and placed crosswise, a cup-shaped magnetic shield fixedly attached to the lower housing in such a manner as to surround the coils, and a dial fixedly attached to arms of the upper housing. The magnetic shield case is provided to protect the coils against an external magnetic field, and it is made of a soft magnetic material having a relatively high coercive force, such as an electromagnetic soft iron (SUY) or a pure iron containing 1% silicon (Si). Because of the material used, the magnetic flux density that remains in the magnetic shield case after the removal of an applied magnetomotive force (i.e., remanence) is considerably high. Thus, if the electric current passing through the coils is cut off while the meter is in operation, the magnet moves to turn the pointer slightly from a position where the pointer was positioned immediately before the removal of the current supply. The remanence in the magnetic shield case also effects the angle of rotation of the magnet even while the meter is in operation, causing a change in the pointing angle of the pointer. To alleviate the above mentioned problems, there is an idea to use a magnetic shield case formed, by drawing, from a blank of a sheet of a material having a low coercive force, such as Permalloy (registered trade mark) containing lead (Pb). However, the use of the Permalloy-Pb alloy as the material of the magnetic shield case causes a considerable cost increase in manufacturing the meters because this alloy is expensive.